1. Field of the Invention
The present invention relates generally to munitions, and more particularly to a speed-adaptive deployable boat-tailing cone for munitions for range extension.
2. Prior Art
Boat-tailing consists of the reduction of the aft cross-sectional area of a flying object in order to reduce drag. Boat-tailing is most effective and critical for supersonic flights. For each speed of a projectile and the flying altitude, there is an optimal boat-tailing angle. For example, if the boat-tailing is two extreme, i.e., the aft cross-sectional area is reduced too rapidly along the length of the flying object, then aft shock becomes too strong, boundary layer separation occurs and drag is considerably increased. If the rate of reduction in the aft cross-section is too slow, then the amount of reduction in the drag is minimal.
At supersonic speeds, the optimal boat-tailing cone angle is a function of Mach number. The boat-tailing angle is the largest at the highest projectile speeds and is gradually decreased as the projectile speed approaches the subsonic speeds. It has been shown that base drag accounts for up to 50% of total drag on a projectile during supersonic flight. With base bleed and boat-tailing, drag in supersonic flight has been shown to be significantly reduced.